Turn on MailTips, including external recipient warnings

Description

MailTips are enabled for the organization with these settings:

• MailTipsAllTipsEnabled: $true;
• MailTipsExternalRecipientsTipsEnabled: $true (warning when a recipient is outside the organization);
• MailTipsGroupMetricsEnabled: $true (group size known to Outlook);
• MailTipsLargeAudienceThreshold: at most {{ large_audience_threshold }} recipients.

Rationale

MailTips show a banner while the user writes the message, before it is sent. The external recipient tip catches the classic mistake of auto-completing a personal or partner address, and the large audience tip catches replies to a whole distribution list. Both are cheap ways to reduce accidental data leaks.

Impact

Users see more banners when writing to external or large audiences. No message is blocked.

Parameters

The value used is your override (tailoring file), else the profile's, else the one of the profile it extends, else the default. Bounds limit what an override may set.

Audit

1. These settings are not shown in the admin centers. Connect to Exchange Online PowerShell as at least a Global Reader.
2. Run (read-only):

   Get-OrganizationConfig | Format-List MailTips*
   

3. Fail if MailTipsAllTipsEnabled, MailTipsExternalRecipientsTipsEnabled or MailTipsGroupMetricsEnabled is False, or if MailTipsLargeAudienceThreshold is greater than {{ large_audience_threshold }}.

Remediation

1. Connect to Exchange Online PowerShell as an Exchange Administrator.
2. Run:

   Set-OrganizationConfig -MailTipsAllTipsEnabled $true -MailTipsExternalRecipientsTipsEnabled $true `
     -MailTipsGroupMetricsEnabled $true -MailTipsLargeAudienceThreshold 25
   

   Replace 25 with the chosen threshold.

Rollback

Set-OrganizationConfig -MailTipsExternalRecipientsTipsEnabled $false.

References

• MailTips in Exchange Online Microsoft, vendor-doc, accessed 2026-10-24
• Set-OrganizationConfig Microsoft, vendor-doc, accessed 2026-10-24
• Maester MT.1039 Maester, tool, accessed 2026-10-24

Mappings

How this control relates to the other framework's: equivalent, stricter, looser, partial or related.

Related controls

• related CB-M365-MAIL-003 Tag messages from external senders in Outlook

People and lifecycle